util/gl: link against OPENGL_gl_LIBRARY on waffle aware systems

Similar to the earlier patch for waffle-less (glut) builds. The need
for this patch became apparent as we removed the libGL link dependency
in waffle.

v2: Try to handle both gl and gles*.

Cc: Mark Janes <mark.a.janes@intel.com>
Reported-by: Mark Janes <mark.a.janes@intel.com>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>